Primality proof for n = 20707:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=29.html>29 is prime.</a>
<br>b^((n-1)/29)-1 mod n = 15608, which is a unit, inverse 8922.
<p><a href=17.html>17 is prime.</a>
<br>b^((n-1)/17)-1 mod n = 4737, which is a unit, inverse 16834.
<p>(17 * 29) divides n-1.
<p>(17 * 29)^2 > n.
<p>n is prime by Pocklington's theorem.